In heavy ion collisions the activity or violence of a collision can be classified by several theoretical constructs [1]}: the number of
nucleons that participate in the collision, \(N_\text{part}\) , by the number of collisions between
participants, \(N_\text{coll}\) , and by the closest distance between the centers of the colliding nuclei, which is called the impact parameter, \(b\) . The term centrality is used as an estimator of the impact parameter of the collisions. It is generally defined in terms of the multiplicity of charged-particles or the
produced in a given \(\eta \)  region.
While in Monte Carlo (MC) simulations \(N_\text{part}\) , \(N_\text{coll}\) , and b
are known, in
data, these variables cannot
be measured directly.
These quantities are estimated using \(\)  or
charged-particle multiplicity, which are both believed to scale monotonically with \(N_\text{part}\)  or \(b\) .
